1. Field of the Invention
The present invention generally relates to a current feedback, and more particularly, to a lighting apparatus with feedback function.
2. Description of Related Art
In the present 3C (computer, communication and consumer electronics) age, the current market is full of diverse and attractive information equipments and various digital means, such as mobile phone, digital camera, digital camcorder, notebook PC and desktop computer, all of which are being developed at a startling pace targeting at providing more convenience, multi functions and pretty looking design.
Most of the information equipments today use a flat panel display as the interface thereof. By means of the display function of a flat panel display, the product can be more conveniently operated. Among the flat panel displays, a liquid crystal display (LCD), due to its advantageous features such as high display quality, small space utilization, low power consumption and no radiation, has gradually replaced the cathode ray tube (CRT) display and became the mainstream display market.
An LCD panel itself has no luminant function, and thus a backlight module is needed to be disposed beneath the PCL panel. The backlight module serves as a high quality and stable light source for LCD display. The LCD display quality largely depends on the design of the backlight module. In particular, the LCD display quality gives an overwhelming effect on brightness and the brightness uniformity of the cathode fluorescence lamp (CFL) inside a backlight module.
U.S. Pat. No. 6,534,934 B1 discloses a multi-lamp driving system, wherein a current-balancing controller composed of passive components is employed to balance and equalize currents of lamps. The proposed current-balancing controller may generate a characteristic error of the multi passive components and cause a mismatch problem. Since the feedback signal is directly provided from the low-side of a single lamp, thus, the feedback scheme is unable to suit multi sets of lamps, which results in a current deviation between the lamp where a feedback signal is taken from and other sets of lamps and, an unequal current allocation to the lamps and insufficient brightness uniformity of the backlight source. In addition, the architecture of the multi-lamp driving system employing the current-balancing controller in feedback mode would largely increase the design cost of a converter and occupy more space on a printed circuit board (PCB).
U.S. Pat. No. 6,717,372 B2 provides another multi-lamp driving system, wherein a current-balancing controller composed of magnetic core components is employed. Similar to the above-mentioned multi-lamp driving system proposed by U.S. Pat. No. 6,534,934 B1, the multi-lamp driving system is unable to feedback lamp currents and encounters the same above-mentioned problems.